Impacts of Vegetation and Precipitation on Throughfall Heterogeneity in a Tropical Pre-Montane Transitional Cloud Forest

Hayden Mahan
School of Meteorology
University of Oklahoma

04 October 2013, 2:00 PM

Precipitation throughfall (TF) plays an important role in the water balance of tropical forests. This study used 129 gauges to measure TF in a tropical pre-montane transitional cloud forest on the Caribbean slope of the Cordillera Tilarán, Costa Rica to quantify TF variability and identify the ecological and meteorological drivers of this variability. Daily TF measurements were taken from 28 June–17 July 2012 and 12 June–16 July 2013, for a total of 39 precipitation events. The mean percent TF for the watershed was 89.5%. TF at individual gauges ranged from 22.7% to 245.7%. Leaf area index (LAI) was calculated above each gauge using hemispheric photography and the mean LAI was 4.9. A statistically significant relationship between LAI and TF was not observed. However, TF was positively correlated with precipitation intensity and TF variability was negatively correlated with precipitation intensity. We additionally determined the minimum number of gauges needed for accurate TF measurements within a 2.2-hectare tropical forest watershed. Random sampling of all 129 gauges indicated that 69 gauges are required to produce a mean within 5% of the true mean TF. This study suggests that the spatial TF variability is highly heterogeneous, and the result of multiple compounding effects.

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